Method and apparatus for processing a minute portion of a specimen

Abstract

A method for detecting a photoacoustic signal includes the steps of modulating the intensity of light obtained from a light source at a predetermined modulation frequency, exciting a specimen by directing the intensity-modulated light onto the specimen, thereby generating a photoacoustic effect in the specimen, detecting the photoacoustic effect generated in the specimen and producing a detection signal indicative of the detected photoacoustic effect, and extracting information about the surface and interior of the specimen from the detection signal, wherein the intensity-modulated light is emitted from an aperture of a near-field optical scanning microscope used in directing the intensity-modulated light onto the specimen while a distance between the aperture of the near-field optical scanning microscope and the surface of the specimen is maintained constant irrespective of the photoacoustic effect generated in the specimen.

What is claimed is: 
     
       1. A method for detecting a photoacoustic signal comprising the steps of: modulating the intensity of light obtained from a light source at a predetermined modulation frequency;   exciting a specimen by directing said intensity-modulated light onto the specimen, thereby generating a photoacoustic effect in the specimen;   detecting the photoacoustic effect generated in the specimen and producing a detection signal indicative of the detected photoacoustic effect; and   extracting information about the surface and interior of the specimen from said detection signal;   wherein the intensity-modulated light is emitted from an aperture of a near-field optical scanning microscope used in directing said intensity-modulated light onto the specimen while a distance between the aperture of the near-field optical scanning microscope and the surface of the specimen in maintained constant irrespective of the photoacoustic effect generated in the specimen.   
     
     
       2. A method for detecting a photoacoustic signal according to claim 1, wherein a scanning tunneling microscope is used in detecting the photoacoustic effect. 
     
     
       3. A method for detecting a photoacoustic signal according to claim 1, wherein light reflected from the specimen surface of light transmitted through the specimen is detected by a near-field optical scanning microscope, and the detected light is used in detecting the photoacoustic effect. 
     
     
       4. A method for detecting a photoacoustic signal according to claim 1, wherein an interferometer which includes a near-field optical scanning microscope is used in detecting the photoacoustic effect. 
     
     
       5. An apparatus for detecting a photoacoustic signal comprising: a light source;   modulation means for modulating the intensity of light from said light source at a predetermined modulation frequency;   exciting means for exciting a specimen by directing said intensity-modulated light onto the specimen, thereby generating a photoacoustic effect in the specimen;   detection means for detecting the photoacoustic effect generated in the specimen and producing a detection signal indicative of the detected photoacoustic effect; and   information extracting means for extracting information about the surface and interior of the specimen from the detection signal produced by said detection means;   wherein said exciting means includes a near-field optical scanning microscope, and wherein the intensity-modulated light is emitted from an aperture of the near-field optical scanning microscope while a distance between the aperture of the near-field optical scanning microscope and the surface of the specimen is maintained constant irrespective of the photoacoustic effect generated in the specimen.   
     
     
       6. An apparatus for detecting a photoacoustic signal according to claim 5, wherein said detection means includes a scanning tunneling microscope. 
     
     
       7. An apparatus for detecting a photoacoustic signal according to claim 5, wherein light reflected from the specimen surface or light transmitted through the specimen is detected by a near-field optical scanning microscope, and the detected light is used by said detection means in detecting the photoacoustic effect. 
     
     
       8. An apparatus for detecting a photoacoustic signal according to claim 5, wherein said detection means is an interferometer which includes a near-field optical scanning microscope.